Statistical analysis
Results and graphics were completed using R software (version 3.6.3). Previous studies have indicated that the yield of pCNV is unrelated to maternal age.31 Therefore, 12730 fetuses with maternal age ≥ 35 years and normal ultrasonography, defined as “fetuses with no identifiable anomalies”, were used as a control cohort for comparison of the yield of pCNV for fetuses with abnormal ultrasonographic findings. The association between ultrasonographic findings and pCNV were performed by Binomial test and Fisher’s exact test with Bonferroni correction. P < 0.05 was considered statistically significant.